Equipment for electochemical collection removal of ions

ABSTRACT

A method and apparatus concentrates, collects and removes heavy metals, other cations, and anions from media permitting generation of electrical fields. The heavy metals and other cations are electrochemically concentrated and precipitated for rapid removal from the aqueous media. The media, which may be aqueous, soils or wastes, is filtered and passed through a cation or anion exchange resin beds. Metals or anions are captured and held in the resin beds. Current is then applied through the resin beds using opposing electrodes of opposite polarity. In the metal removal units, heavy metals and other cations are concentrated around the negative electrode and lifted to a top of the electrode chamber using hydrogen gas lift. The concentrated solution of heavy metals and cations are removed from the chamber above the negative electrode and are circulated to provide additional time for growth and precipitation. Once in a crystalline structure or precipitated form, the elemental metals and metal hydroxides are separated from the aqueous phase using a trap, which retains the crystallates and precipitates. The treated liquid is returned to the chamber beneath the positive electrode for recycling. The anions are concentrated in a similar manner and removed in soluble form from the aqueous media.

This application claims the benefit of U.S. Provisional Application No.60/016,417, filed Apr. 29, 1996.

BACKGROUND OF THE INVENTION

The present invention relates to methods and apparatus for removingheavy metals, other cations and anions from aqueous and non-aqueousmedia.

Existing systems for removing heavy metals include direct currentelectrolytic processes. One of the major deficiencies of direct currentelectrolytic processes is their inability to efficiently remove lowlevel concentrations of toxic anions and cations from aqueous streams.There is a major growing environmental problem of release ofcontaminants into ponds, lakes, surface water, subsurface water, riversand oceans. Toxic heavy metals are not biodegradable and usuallyaccumulate in the environment. One major type of contaminant release isthat of heavy metals from the mining and smelting industries. Runoffwater from operating mines and abandoned mine sites contain both lowlevels and high levels of toxic heavy metals. Those sites oftendischarge the accumulated metal wastes into clean streams, therebycontaminating the streams. Severe environmental impacts result. A stopgap technology most widely used to combat that particular probleminvolves the use of lime for raising the pH of aqueous solutions and forprecipitating the heavy metals. A large volume of sludge is produced inwhich the metals are not concentrated sufficiently to be of interest toa metals reclaimer. That sludge is toxic and accumulates wherever thelimiting process is used.

Existing cation or anion ion exchange units collect heavy metals andother cations on the resin surface until breakthrough of one thosecations or anions is observed. Conventional regeneration of the resinbed usually occurs by passing 1-2 bed volumes of either strong acid,strong base or salt solution through the resin bed. That is followed by4-5 bed volumes of flushing and rinse fluids. Those resin beds aretypically downflow in service and upflow in the regeneration and rinsecycles. Conventional regeneration procedures produce substantialquantities of hazardous fluids. Metal reclaimers are not interested inreclaiming the metals from the regeneration fluids as they are typicallyvery toxic and the concentration of metals is too low for the reclaimerto make a profit.

Needs exist for methods and apparatus for removing metals, cations andanions from water that are environmentally friendly and economicallyfeasible.

Concerns regarding the presence of heavy metals in water supplies arerapidly increasing. Elements such as cadmium, mercury, silver, chromium,lead, copper and zinc exhibit toxicity in humans. The promiscuousrelease of heavy metal and toxic anions into the environment pose greatdangers because of their toxicity and relative accessibility.

Major sources by which heavy metals enter aquatic environments includethe metal processing, metal finishing and plating industries andleachate runoffs from toxic metal dumps. The major toxic heavy metalsgenerated by industrial and mining industries and found in waste waterinclude copper, cadmium, nickel, lead, zinc, chromium, mercury and theradioactive elements radium, thorium and uranium. Related chelatingagents are also found in the waste water, includingethylenediaminetetraacetic acid, nitrilotriacetic acid, citrate,tartrate, gluconic acid and the like. More than 13,000 corporations areinvolved with aspects of metal finishing and electroplating.

A number of specialized processes have been developed to remove heavymetals from industrial waste waters. Processes that have beeninvestigated include: chemical precipitation, ion exchange, solventextraction, cementation, coagulation/flocculation, complexation,adsorption, electrochemical operations, biological operations,filtration, evaporation and reverse osmosis/ultra filtration.

Current state-of-the-art methods for treating plating wastes fromfacilities employ precipitation treatment with conventional hydroxideprecipitation of a mixed waste water in a single reactor. Nearly 75percent of existing plating facilities employ precipitation treatment(primarily hydroxide treatment) as the treatment scheme for removal ofheavy metals from solutions. It is the most widely used processindustrially.

In the hydroxide precipitation process, heavy metals are precipitated byadding an alkali, such as caustic soda or lime to adjust the waste waterpH to the point where the metal exhibits its minimum solubility. Themetals precipitate as metal hydroxides and can be removed byflocculation and sedimentation. The extent of the precipitation dependson the solubility product (K_(sp)) of the metal hydroxide and theequilibrium constants, K_(I) 's, of the metal-hydroxyl complexes. Themetal-hydroxide precipitates can be removed by adequate solid-liquidseparation processes such as sedimentation and filtration. Theeffectiveness of separation is highly dependent on the physicalproperties (size, density, etc.) of those metal hydroxide precipitates.Wide-spread acceptance of the hydroxide treatment is due to its relativesimplicity, low cost of precipitant (lime) and ease of automatic pHcontrol. Sulfide precipitation is an alternative process for removal ofheavy metals due to the low solubilities of the sulfides. Both processesproduce toxic sludges which must be reclaimed or require disposal. Thesulfide process has the potential to generate toxic hydrogen sulfide gasand there are environmental concerns associated with the toxicity ofsulfides.

Limitations of the hydroxide process include the following: precipitatesresolubilize if pH changes; mixed metal wastes require different pHconditions for metals having different precipitation solubilities; thepresence of complexing agents has an adverse effects on metals removal;chromium (VI) is not removed by the hydroxide technique; hydroxidesludge quantities are substantial; hydroxide sludges are difficult todewater due to the amorphous structure; and little metal hydroxideprecipitation occurs below pH of 6.

SUMMARY OF THE INVENTION

The present invention is a method and apparatus for removing heavymetals, other cations, and anions from aqueous and non-aqueous media.The heavy metals and other cations are concentrated and precipitated forrapid removal from the aqueous media. The heavy metals, once in acrystalline structure, are separated from the aqueous phase using atrap, which retains the crystalline precipitates. The precipitatedmetals are recovered as elemental metals or as oxides/hydroxides. Thetreated liquid is always recycled. The anions are concentrated in asimilar manner and removed in soluble form from the aqueous media.

Although the present invention has been developed primarily for use inaqueous media, the present invention is readily modified for use withother applications including conducting gas phase systems and systemsincluding liquids such as hydrocarbons which carry ionic charges (ex.phenols), conducting solids, or any other media or combinations of mediawhich permit ionic mobility in response to an applied electrical charge.Any charged atom or molecule in any conductive media (gas, liquid,porous solid or solid surface) permits transport of an electrical field.

The present invention includes an ion exchange process for collectingthe heavy metals, other cations, and anions on selected resin beds. Therecovery of heavy metals, other cations and anions is accelerated by theaddition of circulating cathodic liquid systems at all resin exchangers.The circulating systems, in conjunction with direct current (DC)electrical systems, supply low level current across both the cation ionexchange resin bed and the anion exchange resin bed. An acidic solutionis generated in the liquid at the anode electrode and a basic solutionis produced in the liquid at the cathode electrode. The combination ofthe flow of liquid in the cathodic recycle and the electrical productionof acids and bases induce rapid electrochemical changes in the resinbeds and strip the heavy metals and anions from the beds. The beds areautomatically regenerated in the stripping process. At the conclusion ofthe stripping process, the cation bed is covered with hydrogen ions andthe anion bed is covered with hydroxyl ions. The soluble heavy metalsand other cations are typically in the acidic pH regime where they arestripped from the resin bed. Liquid cathodic circulation immediatelytransports the soluble heavy metals to a basic pH environment. The largemajority of heavy metals either plate out as elemental metal orprecipitate as oxides or hydroxides. That precipitation is anequilibrium reaction and additional residence time is added to thesystem for continued growth of the flocculated metals/oxides/hydroxides.The additional residence time is incorporated in the design of thecathode precipitation chamber, external cathodic circulating system andthe volume in the heavy metals sedimentation basin (or precipitationtrap). The anions and complex ions acting as anions are concentrated andremoved in either soluble or precipitated form into a removal tank. Thepresent invention has the capability to remove heavy metals and othercations and complex ions that act as cations in concentrated soluble orprecipitated forms.

The high levels of concentration, collection and removal achieved usingthe present invention provides a valuable financial offset to the costof operation. The present invention has immediate application in areaswhere there are either environmental metal concerns (streams, rivers,etc.) and in industries which release metals in waste streams andcleanup of toxic metal holding pits.

The present invention eliminates the need for the lime hydroxideprocess. The present invention concentrates the heavy metals and solubleanion contaminants and does not produce any hazardous liquid or sludgebyproducts. The present system removes heavy metals, other cations andcomplex ions acting as cations as well as soluble anions and othercomplex ions acting as anions from surface water, groundwater, aqueouswaste streams, lakes, rivers and the like.

The present invention uses all classes and types of resins including butnot limited to: strong acid ion exchange resins, strong base ionexchange resins, weak acid ion exchange resins, and weak base exchangeresins. The present invention uses synthetic resins or crystallinesilicates in packed beds or in flow modes for inorganic-contaminantremoval. Particulate resins are usually preferred but other resins maybe used to detoxify a specific raw water. The present invention involvesmetal cation or non-metal anion concentration/phase changes and thecollection of heavy metals that are precipitated according to thestability field of the metal as described by the E_(H) (half cellpotential relative to standard hydrogen) and the corresponding pH(negative log of the hydrogen ion). Metals that are solublebase-precipitated to the crystalline state using the present inventioninclude, but are not limited to, aluminum, antimony, arsenic, barium,beryllium, bismuth, boron, cadmium, calcium, cerium, chromium, cobalt,copper, germanium, gold, iron, lead, lithium, manganese, magnesium,molybdenum, mercury, nickel, palladium, platinum, selenium, silver,strontium, thorium, tin, titanium, tungsten, uranium, vanadium, zinc,and zirconium. Anions removed by the present invention include, but arenot limited to, chromates, sulfates, chlorides, fluorides, carbonates,bicarbonates, nitrates, hydroxyl ions, phosphates and other metal andnon-metal compounds that behave as anions.

The present invention uses the following sequential processes. The firsttreatment is a simple filtration for removal of dirt, detritus and othersuspended matter to prevent the development of a pressure drop acrossthe ion exchange beds. Total dissolved solids, if ionic, participate inthe ion exchange process. The second treatment includes processing thefiltered aqueous raw water containing the heavy metals and other cationand anion mixtures through sequential conventional strong-acid cationexchange resin beds and through strong-base anion exchange resin beds.That treatment removes the large majority of soluble heavy metals andsoluble anions. The process is stopped when breakthrough occurs. Weakacid or base resins are used to selectively remove a financiallyattractive metal such as copper or a radioactive element such asuranium.

The electrodes located above and below the resin beds are polarityreversible, thereby providing the opportunity to remove heavy metalseither from the top or bottom of the resin bed. In preferredembodiments, an upflow concentration system as described below is used.The positive flow-through electrode is positioned immediately below thebottom porous membrane which supports the particulate resin bed. Thenegative flow-through electrode is positioned immediately above the topmembrane of the particulate resin bed. The electrodes are made ofimpervious materials that have been tested for 3 months at 60 amperes ofdirect current at a potential difference of 40 volts in soils. Nodeterioration has been detected.

When cation or anion breakthrough occurs, an electrical/electrochemicalprocess which involves a pH controlled hydroxyl ion recycle is used. Thecombined electrically-derived electrochemical acidic flow rapidlyremoves the heavy metals from the resin bed. The heavy metals flowupward through the top of the resin bed and then through an electrifiedflow-through grid where the electrochemical fluid gradient enters abasic environment above the flow-through electrode. Soluble metals areconverted immediately to either the elemental metal state or anhydroxide state. The soluble metals undergo a phase change (calledelectrochemical dual phase concentration) and the flocculatedmetals/metal hydroxide particles commence growing and are lifted to thetop of the metal concentration chamber by means of a hydrogen gas lift.The gas is composed of very small bubbles of hydrogen which are formedat the surface of the electrified cathode grid which is located abovethe resin bed and at the bottom of the heavy metal concentration andcollection chamber.

The flocculated metals are immediately transported from theconcentration and collection chamber by the cathodic recycle stream. Thecathodic recycle stream originates at the top of the heavy metalconcentration and collection chamber. The recycle passes through theheavy metal and through a metal removal facility which filters out theelemental metals and precipitated metal hydroxides. Secondary metalseparation processes are employed to segregate valuable metals fromnonvaluable metals. Any soluble heavy metals remaining in the treatedliquid recycle stream exiting the heavy metal removal and separationfacility are precipitated in subsequent cycles.

The cathode recycle performs a number of functions critical to thesuccess of heavy metal removal and reactivation of the strong-acid ionexchange resin bed. The cathodic recycle provides growth time for theformation (and size) of the metal precipitates. The total time from thestart of the recycle stream being pulled from the top of heavy metalsconcentration and collection chamber until the time that theprecipitate-free liquid stream exits the heavy metal removal trapprovides a growth period for continued precipitation and enlargement ofmetal hydroxide particles.

A second major function of the cathodic recycle is performed when thehigh pH recycle stream enters the bottom chamber below the resin bed.The positive electrode is located in that chamber. The positiveelectrode is energized with direct current and produces hydrogen ionsand gaseous oxygen. The anode pH is highly acidic. The incoming cathoderecycle stream entry is below the bottom porous membrane of the cationresin bed and below the positive electrode. The mixing of the anodicfluid and the cathodic recycle results in a partial hydrogen andhydroxyl neutralization. The pH increases to a moderate acidity leveland the cathodic liquid recycle moves upwards and into the resin bed.The two forces pushing upward through the resin bed are: the electricalattraction of the positive hydrogen ions to reach the negative cathodeat the top of the resin bed and the more important force of the liftingeffect of the cathodic liquid recycle by increasing the velocity of thehydrogen ions and by rapidly stripping the heavy metals from the activesites on the resin bed surfaces.

If no recycle were employed, the hydroxyl ions would move downwardthrough the resin bed and substantial volumes ofelectrolytically-produced water would be reconstituted by neutralizationwith the upward-moving hydrogen ions. This neutralization wouldconstitute a process efficiency loss. The cathodic recycle prevents anyhydroxyl ions from moving downward through the resin bed, as confirmedby the fact that the underside of the top cathode grid is at amoderately acidic pH. Any early precipitation of heavy metals isprevented by the cathode recycle as the low bed pH preventsprecipitation in the resin bed. When the precipitation is complete, therecycle is reduced and the pH of the anode is lowered for finalreactivation of the resin bed and commencement of the next watertreatment cycle. Note that no toxic precipitates are produced fordisposal. There are no regeneration fluids such as hydrochloric orsulfuric acids. No rinsing or flushing of the bed, which would producemore toxic by-products for disposal, is included.

Removal of the soluble anions from the strong-base anion exchange resinbed and reactivation of resin are similar to the removal of heavy metalsfrom the cation resin bed. The major difference is that the majority ofanions remain soluble throughout wide pH ranges and require removal in aconcentrated solution. The solution, as provided in the presentinvention, includes the novel usage of the basic cathodic recycle. Inthe case of anion removal, the positive flow-through electrode islocated above the top of the anion resin bed and the negativeflow-through electrode is located at the bottom of the anion resin bed.

The cathodic recycle is pulled from below the bottom of the cathode andinjected above the top of the positive electrode. The largest fractionof the hydroxyl ions travel upwards through the resin bed counter to thedownwards flow of the cathodic recycle. The cathodic recycle removes thebalance of the hydroxyl ions from below the negative cathode and injectsthe hydroxyl ions above the top bed positive electrode. A basicenvironment is maintained above the positive flow-through electrode. Therecycle is adjusted to prevent the production of water through theupward flow of any hydroxyl ions into the resin bed and for preventingcontact with the downward-moving acidic hydrogen ions. The counter-flowupward movement of the hydroxyl ions through the resin bed sequentiallyremoves the negative anions from the ion exchange sites. The resin bedis initially pH-acidic and is slowly converted to pH-basic as theupward-moving wave of hydroxyl ions increase the resin bed pH. Thenegative anions move upward, counter to the downward liquid flow of thecathodic pH recycle, and are concentrated in the upper chamber above thepositive top electrode. The anions are typically recovered as aconcentrated liquid.

Anion concentrations easily reach levels 100 times greater than originalraw water anion concentration levels. The concentrated anion material isremoved to an anion collection tank for disposal or further processing.Note that no toxic recycle fluids are generated for disposal except fora small volume of concentrated anodic fluids. (One example was that theoriginal 4,000 ml of a toxic raw water containing sulfate and chlorideanions was concentrated to a final volume of 40 ml). The rate of thecathode circulating fluid is adjusted until the entire bed pH is at anelevated pH. The anion resin is completely reactivated and a new rawwater treatment cycle is repeated.

A comparison of the present invention with the lime hydroxide processclearly evidences the benefits realized using the present invention:

If the pH changes in the lime hydroxide process, resolubilizationoccurs. In the present invention the pH remains steady and noresolubilization occurs. There is no liming in the present invention.

The use of lime hydroxide with mixed metals is difficult becausedifferent metals of different solubilities require different pHconditions. The present invention covers the entire pH range where heavymetals precipitate.

Unlike the lime hydroxide process, the present invention has thecapability, by electrical and electrochemical means, to extend the pHrange as required for special metal precipitations.

The presence of complexing agents in the hydroxide process has anadverse effect on metal removal efficiency. The present invention doesnot use any completing agents.

Chromium (VI) is not removed by the lime hydroxide process. In thepresent invention, the CrO₄ ²⁻ ions are readily removed using an anionresin and then concentrated in soluble form. The chromate ions areelectrolytically reduced to soluble Cr(III) ions and those ions arecathodicly concentrated or cathodicly plated as chromium metal oxides.The present removal methodology has been demonstrated in bench scaleexperiments.

Cyanides interfere with heavy metal removed via lime-hydroxideprecipitation. The present invention treats all electrolyticallyproduced gases, including hydrogen cyanide, hydrogen chloride, hydrogensulfate, nitric acid and the nerve gases stibine and arsine as well asother non-organically derived poisonous gases. All cation and anionunits are equipped with caustic scrubbers on every gas stream. Scrubbersare discrete units and are complete with valving and equipment to insureall hydrogen and oxygen gases are separately treated.

Lime-hydroxide sludges are difficult to dewater. No lime sludges areproduced using the present invention.

The lime-hydroxide process does not precipitate metals at pH values lessthan 6. The present invention precipitates heavy metals from a pH rangeof 4 and higher.

The present invention is applicable in many fields and applicationsincluding, but not limited to, removal of high levels of nitrates fromgroundwater contaminated by agricultural fertilizers, removal ofradiological substances (radionuclides, radioactive complexes) fromgroundwater, recovery of plating solutions from closed loop processes,replacement/reduction/treatment of alkylation sludges from petroleumrefineries, removal of lead from drinking water, removal of arsenic fromgroundwater, and removal of chromium (VI) from groundwater.

The present invention is applicable for any charged atom or molecule inany conductive media (gas, liquid, porous solid or solid surface).

The present invention is a method and apparatus for use in aqueous mediafor the electrochemical dual phase concentration, collection, andremoval of heavy metals, other cations, and complex ions that act asheavy metals. The present invention also includes methods and means forremoving anions and complex anions that act as anions. In addition toaqueous media applications, the present invention is operable innon-aqueous conductive media including but not limited to gaseous,liquid, porous solid and solid surface media. The present invention iscapable of removing both low and high concentration of toxic heavymetals and anions from surface waters, ground water and releases fromsystems containing heavy metals and toxic anions. Low concentrations ofa few mg/l of heavy metals up to almost total solubility may be capturedusing the present invention.

Electrical and electrochemical derived transport and liquid chemicalgradient changes are used to achieve highly efficient concentration,precipitation and collection of heavy metals and toxic ions. Changes inchemical gradients are used to partition the precipitated heavy metalsinto separate heavy metals, groups of contiguous heavy metals, separatemetal oxides/hydroxides, groups of contiguous heavy metaloxides/hydroxides and other groups where heavy metals are precipitatedas chlorides, sulfates, carbonates, nitrates, fluorides and any otherprecipitating anions. Heavy metals and radionuclides are alsoselectivity concentrated, collected and recovered using the presentinvention.

The present apparatus includes resin beds, membranes, electrical gridsand a raw water filter for removing remove dirt and other particulatesto prevent fouling of resin beds. The resin beds include alternativetypes of resins designated strong, basic and weak and are made ofconventional materials. Activated alumina adsorption is included forselectively concentrating specified metals or radionuclides. Theelectrical grids provide efficient sources of acid (hydrogen ion) andbase (hydroxyl ion) for initiation of a baseline concentration,collection and precipitation process for removal of heavy metals, andradionuclides and for commencing concentration and collection of solubletoxic anions.

The present invention includes electrochemical cathodic and anodiccirculating systems for increasing removal efficiency. The cathodiccirculating system generates a liquid chemical gradient which permitsrapid removal of heavy metals from the resin bed without any fouling ofthe resin bed and constitutes the major feature of the dual phase heavymetal removal from the resin bed, concentration of the heavy metals andexternal collection of the precipitated heavy metals. The cathodicliquid recycle is used in conjunction with electrical/electrochemicalgradients to flocculate, precipitate and partition the heavy metals intoindividual and/or contiguous groups such as elemental states,oxides/hydroxides, and other element precipitations such as sulfates,chlorides, nitrates, carbonates, bicarbonates and any other anion state.The chemical gradient is basic on one side of the electrode and acidicon the other side of the electrode. The range of chemical gradient mayvary from strong acid to strong basic for precipitation of heavy metals.The cathodic liquid recycle recovers the heavy metals in either solublestates or precipitated states. In preferred embodiments, the cathodiccirculating system operates in such a direction that heavy metals abovethe resin bed cathode are always at a basic pH while the resin bed is atan acid pH. Anions collected above the resin bed anode are always at abasic pH while below the anode the liquid is at an acidic pH and theresin bed is at a basic pH. The resin beds do not foul readily as heavymetals attached to the resin bed are in a soluble state and heavy metalsare flocculated above the resin bed top cathode. Thus no flocculatedmaterials enter the resin bed in a solidified form that would lead tobed fouling and drop in process efficiency.

The present invention further includes an external removal system thatis directly tied into a stationary or portable filter trap forcollecting the precipitated metals but not the ionic liquids. Thestationary or portable trap is noncorrosive and has a capacity forcollecting hundreds of pounds of metal hydroxides. The stationary orportable filter trap may be replaced by a partitioned collection systemwhich includes several compartments, with valuable heavy metalspartitioned in designated compartments and nonvaluable heavy metalscontained in other designated compartments. That partitioning ispreferably conducted by automatically switching or partitioning heavymetals to designated compartments by means of computer controlledmonitoring of designated process variables.

Minute bubbles of hydrogen gas are formed at the top of the cathode toprovide a gas lift for the precipitated heavy metals. The collectedheavy metals are easily removed from the top dual phase heavy metalsremoval chamber.

The present removal system permits continued growth of heavy metalcrystalline hydroxide structures and increases heavy metal concentrationefficiency. The concentration and removal of soluble anions from theanion resin beds is enhanced by a continuous circulation of caustic oracid for measured concentrations up to 10-30 times originalconcentrations.

The electrical grids are preferably made of impervious materials that donot dissolve, decay or become coated with non-conductive materials. Theresin bed porous filters or membranes perform the function ofcontainment of the particulate resin inside the resin beds. Scrubbersfilled with caustic are included in the oxygen and hydrogen gas lines toneutralize all produced gases formed during theelectrical/electrochemical production of hydrogen and oxygen from toxicraw water sources.

Preferred embodiments of the present invention include computerassessment and control of key process variables in switching the aqueousor other ion charged media into the service or treatment mode and inswitching the treated water or other charged media into the dual phaseremoval/soluble mode removal of the heavy metals or contaminants fromother charged media as well as anions collected on the resin beds. Thecomputer control operates the heavy metal partitioning system whenrequired. The monitors and simple analytical equipment provides inputfor computer assessment and process control.

A pH control system is preferably included for controlling the liquidrates of the circulating cathodic recycle and the liquid rates of thecirculating anodic recycle for enhancement of the removal of the heavymetals cations, other cations and complex ions that act as cations aswell as anions and complex ions that act as ions.

In preferred embodiments, the present invention is portable and isskid-mounted for location at raw water processing sites. Portableelectrical equipment such as arc welding machines are substituted inlocations where no permanent AC electrical facilities are available.

The vessels and piping of the present invention are constructed forpreventing the grounding of the electrodes and the reduction or loss ofthe production of the electrical/electrochemical transport and chemicalgradients required for removals of heavy metals, radionuclides andanions.

These and further and other objects and features of the invention areapparent in the disclosure, which includes the above and ongoing writtenspecification, with the claims and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a metal removal unit of the present inventionin a service mode, where heavy metals are concentrated and exchangedwith hydrogen ions.

FIG. 2 schematically shows a metal removal unit of the present inventionin a heavy metal dual phase removal mode including cathodic recycleenhancement.

FIG. 3 schematically shows an anion exchange unit of the presentinvention in a service mode, where anions are concentrated on anionresin in exchange for hydroxyl ions.

FIG. 4 schematically shows an anion exchange unit of the presentinvention in an anion concentration and recovery mode including cathodeto anode recycle.

FIG. 5 schematically shows an accelerated removal of heavy metals usinga unique charge balancing system and indicates that heavy metals can beremoved at 3-5 times the rate of existing standard electrokineticremediations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a metal removal unit 1 of the present invention whereinheavy metals are concentrated and exchanged for hydrogen ions. Raw water3 enters through the top 5 of the cylindrical vessel 7 and enters theraw water chamber 9. The raw water 3 has been previously filteredthrough a conventional inlet filter 11, such as a cartridge, a sand bed,or the like, to remove dirt, grit and suspended matter prior to entryinto the raw water chamber 9. The raw water 3 passes through the topcircular electrode grid 13. Grid 13 is not electrified during theremoval of soluble heavy metal ions. Grid 13 is made of materials whichare virtually impervious to all acids or bases. Grid 13 is located abovea first porous membrane 15 which covers the top of the resin bed 17. Noion selective membranes are required. A second porous membrane 19 islocated at the bottom of the circular bed 17. The membranes 15, 19prevent resin from escaping from the cylindrical resin bed 17 and alsoprevents sources of particulates from entering and fouling the resin bed17. The metal-contaminated water flows in a downflow configuration;upflow designs result in channeling, with resultant low efficiencytreatment and early breakthrough. A bottom electrode grid 21 ispositioned beneath the second porous membrane 19. The bottom electrode21 is not electrified during removal of soluble heavy metal ions. Theembodiment of the present invention shown in FIG. 1 is an operatingbench scale unit where tests have been performed on both raw andsynthetic waters over a range of individual cation concentrations from 5mg/l to 2,000 mg/l.

The reaction which occurs at the surface of the resin particles is anequilibrium reaction. The typical service flow is 0.5 gallons/minute percubic foot of resin bed with a maximum service flow of 1.0gallons/minute per cubit foot of resin bed. Rates in excess of thoselisted above have been confirmed by laboratory test work. The resin usedfor heavy metal removal is preferably a strong-acid ion exchange resinthat is beige in color, opaque, has a structure that is macroporous andcrosslinked with polystyrene, and has a sulfonic acid functional group.When the raw water flows through the resin bed, the heavy metals have astronger affinity for attachment to the resin and accordingly displacethe hydrogen ions. The treated water is slightly more acidic than theraw water as a result of the replacement of acidic hydrogen ions byheavy metals. This replacement can be tracked as a wave of aciditymoving downwards through the resin bed. When the sites have been filledwith heavy metals, the incoming heavy metals will start leaking throughthe exit (bottom) of the resin bed. This phenomenon is calledbreakthrough and the process is stopped at this point.

The present invention further provides for the electrochemicaldual-phase removal of the metals. The present invention generates veryhigh concentrations of the recovered heavy metals and involves use ofless than 5 percent of the regenerants (acids, flushing and rinsing)used in conventional regeneration.

As shown in FIG. 2, operation of the dual phase removal is as follows.All inlet raw water valves and outlet treated water valves are closed.The electrodes 13, 21 are energized, with the positive electrode 21below the bottom porous membrane 19 and the negative electrode 13 abovethe upper porous membrane 15. Switching the polarity of the electrodes13, 21 also works but is more cumbersome. The current level is very lowand no significant heat is generated so that the integrity of the resinbed 17 is protected against thermal stress. Power levels are raiseduntil slight gassing at both electrodes 13, 21 is observed. The pH ofthe anodic fluid in the reservoir 23 below the anode and the pH aboveand below the cathode are monitored until the anode reservoir 23 reachesa specified low pH and the liquid above the cathode reaches a high pH.

In inefficient conventional prior art processes, the only way that theheavy metals can be removed is to use high currents at the positiveelectrode so that hydrogen ions are produced to electrically strip theheavy metals from the cation resin bed. When electrical gassing occursat the electrodes, the maximum hydrogen ions and hydroxyl ions areproduced at the positive and negative electrodes, respectively. Thatproduction of gas at the electrodes is an electrical inefficiency. Afurther inefficiency of prior art processes is that in a cell of thatconfiguration, the small hydrogen ions move upward faster than thehydroxyl ions move downwards and those ions meet at approximately 2/3distance from the anode and one third distance from the cathode and formmolecular water. That formed water contains very few ions and does notconduct an electrical charge and adds to the cost of regeneration.

The present invention removes the soluble heavy metals more quickly fromthe resin bed 17, immediately precipitating the heavy metals andcompacting the precipitates into a concentrated valuable by-product ofheavy metals without having the disposal problem of large volumes ofconventional waste by-products.

The present method uses a cathodic recycle enhancement system. FIG. 2shows the present system which pulls precipitated heavy metals from thevolumetric area above the negative electrode 13. The precipitated heavymetals flow through a solids trap 25 where the elemental metals andmetal oxides/hydroxides are removed. The resultant clean cathodic liquid27 exits the trap and flows into the bottom of the anodic liquidreservoir 23. There is an optimum range where heavy metals willprecipitate into crystalline oxides or hydroxides and this range istypically 4-12 pH. The cycle can be described as follows. Anodic liquidat low pH is pressured upward through the resin bed 17 (reverseelectro-osmotic effect) which accelerates the anodic liquid upwardthrough the resin bed and more uniformly removes the heavy metals 3-5times faster than by the simple conventional prior art processesdescribed above.

In a standard electrical regeneration of a cation resin bed, thehydroxyl ions move through the resin bed and either form water asdiscussed earlier or raise the pH sufficiently to precipitate some heavymetals in the upper third of the resin bed. That precipitation istypically found in electrokinetic soil remediations of heavy metals. Thepresent cathodic recirculation literally solves all the problems whichhave been discussed, produces a valuable byproduct, and improves thequality of the environment. When the cathodic circulation enhancement isinitiated, a flow of metal-enriched precipitates 29 circulates from thespace above the cathode 13 (Dual Phase Heavy MetalCrystallization/Removal) and into the precipitated heavy metals removaltrap 25. The trap 25 is preferably a portable filter, a sedimentationunit or other similar device which fills up with the crystalline metals.The liquid in that trap 25 is syphoned and returned to the circulatingsystem. The trapped metal solids are removed or a new portable trap isinstalled. The trapped metal solids are forwarded to a metals reclaimer.

The filtered caustic solution 27 is injected into the bottom of theanode compartment 23 below the resin bed 17. As a result of thecirculating cathodic liquid, the hydroxyl ions do not enter the resinbed 17 and the pH just below the bed 17 stabilizes. As the soluble heavymetals are pushed upward through the cathode grid 13, immediateprecipitation occurs. The small bubbles of hydrogen gas also play animportant role in collection and flocculation of the heavy metalprecipitates which form above the energized cathode grid 13 and improvethe rate at which the cathodic recycle transports the crystalline metalsfrom the top chamber 9 into the metals removal trap 25. When theprecipitation of the circulating fluid ceases as the fluid enters thespace above the cathode zone, it is assumed that all exchangeable resinsites have exchanged the heavy metal for hydrogen ions. At this pointthe pH of the bed 17 may be checked to insure that the pH is low anduniform throughout the resin bed 17. A uniform pH condition throughoutthe resin bed 17 confirms that the bed is ready to receive anothercharge of raw water and the sequence is repeated. The treated cationwater is either sent to the strong-base ion exchange resin bed or storedin an intermediate tank. Where multiple resin beds are available, modesof total continuous flow for removal of cations and anions is readilyderived.

Special precautions are required when working with aqueous liquidscontaining cyanides, arsenic, antimony and fluorine compounds, as thereis the potential for production of toxic gases such as hydrogen cyanide,arsine, stibine and hydrogen fluorides. As shown in FIG. 2, causticscrubbers 31 are located on both the hydrogen and oxygen vent lines 33.The caustic scrubbers 31 scour the hydrogen and oxygen gases during theregeneration of the resin. The presence of the cyanide ion may producesmall quantities of hydrogen cyanide which are neutralized by thecaustic scrubber.

FIG. 3 shows the anion exchange unit 41 in service mode where anions areconcentrated on anion resin in exchange for hydroxyl ions. The stronganion exchange resin used is preferably white cellular crosslinkedpolystyrene having a quaternary amine functional group. That resin isfirst treated with a strong solution of caustic soda in order to replacethe chloride ion with the hydroxyl ion. The regeneration toxicby-products include 6% strong caustic solution and the 2-3 bed volumesfor bed washing and rinsing. Those toxic regeneration solutions areconsidered to comprise a significant disposal problem. The presentinvention uses an electrical current to generate hydroxyl ion andactivate the resin in one step. Thus all the chemical regenerants listedabove have been eliminated from the regeneration process and asignificant waste disposal problem has been eliminated.

The untreated anion water 43 is added at the top 45 of the strong-baseanion resin bed 47 in the downflow service mode. Breakthrough (leachingof one or more of the anions into the treated water) is determined bythe relative affinity of the anions to displace the hydroxyl ion.Breakthrough testing is performed to determine if one or another of theanionic species is in the treated outlet water. An assortment ofsurrogate tests are available for anion presence. The tests provideindications of bed saturation or breakthrough. Raw water testing isperformed to determine the species and concentrations of anions ofinterest in a specific raw water. When breakthrough of the criticalanion occurs, the ion exchange service mode is halted and the anionexchange bed is converted to the anion exchange, anion concentration andresin recovery mode.

FIG. 4 describes the regeneration scheme of the present invention. FIG.4 shows the steps necessary for rapid removal of the soluble toxic anionconstituents. The valves are closed on the inlet and outlet of the anionresin bed. The polarity of the bottom flow-through electrode 49 isnegative and the polarity of the top flow-through electrode 51 ispositive.

The cathodic recycle recirculation is started by pumping caustic frombelow the negative electrode 49 at an elevated pH. The bottom cathodecompartment 52 liquid remains clear and bright throughout the anionremoval and concurrent reactivation of the anion exchange bed. The topzone 53 above the positive electrode 51 becomes "murky" which indicatesthat the rapidly increasing number of anions released from the resin bedare accumulating in the top liquid chamber 53 above the anode. Themurkiness may also be partly due to a slight insolubility of the anionsat the elevated pH. When the recirculation system is in equilibrium withhydroxyl and hydrogen ions generated from the DC power supply, the pHvalues in the system are relatively constant. The hydroxyl ions split,with some travelling upwards inside the resin bed and dislodging thenegative anions, which immediately accumulate around the top positiveelectrode 51. A fraction of the hydrogen ions are neutralized by thecaustic stream which is being added above the positive electrode 51.This prevents any significant acid front of hydrogen ions movingdownwards into the resin bed and preventing removal of the anions. Theconcentrated anode electrode fluid 55 which may contain anionconcentrations at 10-100 times the original anion concentration arecontinuously or intermittently pumped into the concentrated anion tank57 or other container, as shown in FIG. 4.

A bench test of an anion concentration and removal unit for removal ofchloride and sulfate ions is described below. In this particular test,the pH of the bed started rising from the bottom of the bed as hydroxylions replaced chloride or sulfate sites. Reactivation of the resin bedwas caused by upwards mobility of the hydroxyl ions and removal of thesulfate and chloride ions. The target anions had all been removed andreplaced by hydroxyl ions. The original 9,200 mg of total sulfates andchlorides was contained in 4 liters and the 8300 mg recovered was in avolume of 40 ml. Thus the retained concentration of the unwanted anionswas increased from 2,300 mg/l to 207,500 mg/l. The treated aqueoussolution was reduced to 225 mg/l of total soluble sulfates and chloridesfor a significant improvement.

The present invention has applications for electrically enhancedsaturation of lime slurries (calcium hydroxide) where fluorides areprecipitated in a lime slurry. The solubility products for lime andcalcium fluoride are extremely low and tests are now underway to providean electrical stimulus which motivate the fluoride ions to quicklysaturate and precipitate with the lime. A more rapid precipitationreduces lime costs and achieves a cost reduction in hazardous wastedisposal. That item is of general interest to the petroleum refiningindustry worldwide. The positive electrode is placed at the bottom of asettled lime slurry bed and the negative electrode is placed at top ofthe of the decanted liquid which is in the same container above thesettled lime bed. When the electrodes are energized, the top negativeelectrode pushes the fluoride ions in the direction of the slurry andtowards the positive electrode located on the underside of the slurry.As soon as the fluoride level reaches an acceptable low level, theliquid decant is sent to the waste water treatment plant without furthertreatment. The enhancement described above temporarily increases thesolubility product of calcium fluoride by a more uniform precipitationof fluoride ions.

Brief Description of Bench Scale Heavy Metals and Anion Removals

A hazardous synthetic water was prepared to simulate the Berkeley Pit inMontana. The cations were readily removed in 1.5 liters of water whichflowed through a resin bed of 84 cubic cm. The dual phase recoveryprocess indicated that more than 90 percent of the predicted heavymetals (iron 1,000 mg/l) were removed.

Cations and anions were removed from second mine wastewater. The cationof interest was iron (150 mg/l) and was totally removed.

Electrolytic removal of chromium as Cr(VI) from sandy soil containing aconcentration of over 10,000 mg/l chromium produced the followingresults. Initially the negative chromate ions congregated near thepositive electrode. Anodic reduction reactions converted a fraction ofthe chromate ions to Cr(III). Forty-five percent of the Cr(III) ionswere removed in the concentrated cathodic liquid as Cr(III). It isassumed that soil reactions prevented conversion of all the Cr(VI) ionsto Cr(III) ions.

Equipment and Devices

Preferred embodiments of the present invention preferably include thefollowing parts.

Resin containers/Piping and Valving. These vessels are preferably madeof plastic, non-conductive materials, non-grounding materials or metaltanks that are lined internally with non-conductive coatings. Piping andvalves are preferably made of plastic or plastic-coated metals. Thecontainer traps are preferably made of plastic or combinations of metalsand plastics. Pilot units use one cation exchange resin unit or oneanion exchange resin unit, one cation and one anion exchange resin unit,and any multiple of cation and anion exchange resin units. The numberand type of units is dependent on the ionic raw water concentrations ofcations and anions. Resin bed size is not restricted and contains anyquantity of resin provided by resin manufacturers as long as maximumprocess flows, minimum bed area and minimum bed height are met. Forsmall applications, swimming pool filters are readily converted to resinexchange beds in the capacity range of 10-30 cu. ft. Possible plasticsinclude, but are not limited to, Teflon, high strength polyethylene, andpolypropylene high strength injection-molded vessels, fiberglass,non-conducting plastic linings, and the like.

The placement of electrodes, electrode materials, sizes of cathodic andanodic liquid chambers, dynamic liquid/solid removal designs, auxiliaryequipment for partitioning of flocculated heavy metals/oxides andhydroxides, partitioning of soluble heavy metals, partitioning andseparating of soluble and/or insoluble anions are important features ofthe present invention.

Computer data assessment preferably includes any or all of the followingcritical process variables including: temperatures of raw water andtreated waters; temperatures of resin or dual phase regeneration beds;temperatures of cathodic or anodic recycle flows; breakthroughidentification monitors; turbidity monitoring of raw and treated watersand any soluble cations or anions produced in the electrochemicalregeneration process; pH measurements of cathodic or anodic recycles; pHmeasurements of resin beds in water treatment mode and electrochemicalregeneration mode; pH measurements of recovery, collection, andsegregation of heavy metals and anions; pH monitoring of thepartitioning equipment for segregation of precipitated heavy metals, andother anions and radioactives; conductivity measurements to determineresin bed saturation or degree of removal of anions or cations from theelectrochemical regeneration; monitoring of pressure drops across inletfilters, resin beds, electrochemical regeneration and heavy metalsprecipitation; and equipment for weighing of heavy metal collected inthe partitioned and flocculated heavy metal recovery containers (e.g.zinc-rich, copper-rich and iron-rich oxide/hydroxide ores). The abovelisting shows only a partial collection of monitoring and controlvariables and is a non-exclusive and partial listing of processvariables that may be used in equipment automation and improvedautomated separation of byproducts.

The small caustic scrubbers on the vent gas lines at cation and anionion exchange resin beds are preferably constructed of durable plastic or316 lined stainless steel or fined monel-grade steel. All materials arehighly resistant to strong acids and bases.

Power supplies for the present invention preferably include alternatingcurrent (AC) converted to direct current (DC) devices and include allinlet power sizes from 110 volt AC to 110 volt DC up to 440 volt AC to440 volt DC and small bench top laboratory units up to field scale size.If power is not available at a remote location, then AC/DC dieselpowered arc welding machines are used where suitable fuel is available.

Current strength is an independent variable and is held constant whilethe dependent variable voltage registers the potential differencebetween the positive and negative electrodes. As stated earlier,impervious electrodes are used in the present invention to avoidpossible scaling or dissolution of the electrodes. Electrode gridsshould always face each other and expose the largest surface area forhighest efficiency. All equipment is automated with specific controlequipment used for each type of water to be treated.

The present invention is very simple and well suited to automation andremote operation. The present invention may be installed, for example,in mine tunnels and at remote locations where operating sequences aretransmitted by satellite.

The present invention is applicable to all hardness classifications.Typical raw waters are in hardness ranges greater than 300 mg/L ofCaCO₃. The present invention precipitates and flocculates heavy metals,with collection, compression, and partitioning of the crystalline metalsin portable or stationary containers for transfer to metal reclaimers.

The present invention removes soluble metals and soluble salts of metalsin an effective and efficient manner. The present invention isapplicable to broad and high ranges of concentrations of minerals andmineral complexes. The present invention offers a means of recovery ofthe valuable minerals and segregation and sales of these valuableminerals and achieves an overall reduction in waste volume from theprocess.

The present invention uses produced hydrogen ions for acceleratingremoval of the soluble heavy metals from the surfaces of the cationresin bed and converts the energy to produce recombined water intoelectrochemical gradients which will be used to separate heavy metals byprecipitation. FIG. 2 shows the continuous cathodic high pH causticrecycle which flows from the top of the dual phase crystalline heavymetal chamber and enters below the electrified anode. The upward flowdrives the produced hydrogen ions up through the resin bed while at thesame time preventing a fraction of the hydroxyl ions from travellingdown into the resin bed and forming water. As the upflow of acidicliquid passes through the cathode there is an immediate electrochemicalgradient change in pH. Above the cathode an electrochemical basicincrease in pH results. A hydrodynamic effect is observed whichsignificantly improves the precipitation of the heavy metals. Thecontinuous caustic recycle performs another important function of actingas a carrier fluid in moving the precipitated metals into the metalsremoval trap and returning the clean fluid into the bottom of the resinbed. An additional benefit is that the heavy metal precipitationreactions are not instantaneous and the volume of line and metalsremoval trap capacity increases the overall heavy metal removalefficiency.

The present invention uses the largest area of the positive electrodefacing the largest area of the negative electrode. That arrangementachieves the lowest electrode current density for the input current andvoltage applied. Other arrangements tend to lead to higher electricalcosts, misuse of equipment and failure of the anode through either heavyscaling or dissolution of the anode itself. The anodes should not beplaced in the resin bed. The resin is heated and operates at reduceddemineralization efficiency, causing an additional risk of resincollecting and baking onto the anodes. Current efficiency declines andreduces the production of the caustic and regeneration intervals areextended and demineralization capacity is reduced.

As shown in FIG. 5, the present invention removes heavy metal cationsfrom soils and wastes and collects those soluble heavy metal cationsmuch faster than by current electrokinetic technology. The resin bedsare rapidly loaded with heavy metals. A new lightweight silver electrodeis used for anode and cathode positions in the soil beds. The silverelectrodes are made using rare-earth iridium catalyst coated titaniumgrid electrodes in slim rectangular form. The electrodes have the uniquecapability of operating at very high current densities.

Computer acquisitioned data is assessed by a proprietary computer dataacquisition program to monitor variables in soil and liquids. Sensorsused include but are not limited to air temperature, time, inputvoltage, input amperage, power, soil site voltage, liquid flow monitors,soil pH, conductivity, soil surface and downhole temperatures, percentmoisture of soils, charge balancing electrode pH, resistivity of soiland the like.

As shown in FIG. 5, the unique charge balancing system 61 includespumping the liquid using a pump 63 from the cathode chamber 65 at ratesappropriate to soils or wastes designated as sandy, clayey sand, sandyclay, clay, peat and the like. The rates may vary from 10-1,000 gallonsper hour depending on soil or waste type and size. The cathode 69becomes a secondary anode and pH is maintained at about 2.0-2.5. The lowpH prevents significant plating on the secondary anode 69, and nosludges form at the low pH. Level control is maintained at the cathode69 (or secondary anode) to insure a static height in the cathode chamber65.

FIG. 5 schematically shows the component parts of the Charge BalancingSystem 61 in the present invention for accelerated removal of heavymetals from a contaminated soil or sludge waste. A positive electrode inthe contaminated soil or sludge waste 71 a negative electrode 69 in thecathode chamber 65 in the contaminated soil or sludge waste, a pumpingunit 63 to move the soluble metal-laden liquid 75 from the negativeelectrode chamber, through the particulate removal filter 73 and intothe strong acid cation resin bed 81. The cleaned liquid 83 which flowsthrough a pH controller 77 which adjusts the pH of the circulatingliquid to a range of 2.0-2.5 pH and returns the acidic liquid to theanode 3. The low pressure zone created in the vicinity of the cathode bythe pumping unit 63 starts removing the liquid and lowers the liquidlevel in the cathode compartment 69 coupled with the high pressurecreated at the anode 71 results in initiation of an increasing liquidflow over the above circuit. The anode 71 is equipped with a high/lowlevel flow controller and excess acidic liquid will be distributed atthe surface in the vicinity of the anode. The cathode is equipped with ahigh/low level flow controller which maintains a liquid level of notless than three fourths of the cathode compartment. The total liquidflow is continually increasing across and throughout the contaminatedsoil or sludge waste site as time passes.

The secondary anode 69 is a cathode and still has a negative charge atthe surface, but the charge balancing system 61 depresses the pH andprevents plating and the production of sludges in the cathodecompartment 65. Additionally, as the rectangular silver electroderemains clean, there is no loss in applied DC power efficiency, and siteremediation costs will be cheaper. A flow controller at the primaryanode prevents overflow at the primary anode 71.

The flow 67 from the secondary anode 69 passes through a particulatefilter 73, which removes any precipitated compounds and/or soilparticulates, if needed. An optional activated carbon filter is employedif organic compounds (chelating agents) are present in the site fluids.The pumped fluid from the secondary anode circulating filter 73 entersdownflow into the proprietary strong acid heavy metal ion exchange unit75.

In the first stage the proprietary ion exchange unit 75 collects solubleheavy metals at a low pH. The unit 75 can use most commercial resins,and the soluble heavy metals are captured on the activated resin bedsites in order of the relative affinity of the particular heavy metalfor the particular resin. The site exchange reaction involves theremoval of hydrogen ions which are replaced at the activated resin sitesby the heavy metals. The special ion exchange unit 75 concentrates andcollects the metals as part of a two stage process metal collection andresin bed regeneration process. The outlet fluid 77 from the resin bedion exchange unit 75 is relatively free of metals.

The outlet liquid 77 with its pH adjusted through the pH controller 79is returned to the anode 71. Either mineral acids or organic acids maybe used, depending on regulatory requirements for environmentalprotection of the soils in the site. The circulating liquid systemvolume can vary from 50 to 100 times faster than the fluid flow from aregular electrokinetic cell which uses only electro-osmosis andelectromigration to move the fluid through the soil bed. The circulatingliquid returns to the anode 71 at approximately the same acidity as theanode 71. The heavy metals have been removed in the resin bed 75, andthe anodic acid flow is capable of removing heavy metals atsignificantly increased rates when compared to removal rates ofconventional electrokinetic processes.

When the ion exchange bed 81 is full of metals and breakthrough (exitliquid 83 from the resin bed contains small traces of the heavy metals),the inlet heavy metal-laden liquid flow will be switched to a standbyion exchanger containing regenerated resin and new resin exchanger 79will be placed in service and the original ion exchange unit 81 will beregenerated. The heavy metal regeneration products will be sequentiallyplaced in containers which contain metal-rich fractions of commercialmetals. There is no liquid waste produced. The silver electrodes usedsustain a high current density and are not prone to metal plating orfouling, thus maintaining a high electrical efficiency.

The heavy metal removal rates from the same site using standardelectrokinetic technology and utilizing electro-osmotic andelectro-migration forces, are only a small fraction of the heavy metalsremoved by the charge balancing process. The soluble concentration ofremediated heavy metals are lower using standard electrokinetictechnology. Partial plating of metal mixtures and precipitated metaloxides/hydroxides occur at the cathodes. Complex gravity sludges whichcontain metal mixtures as well as soil fractions are deposited in thebottom of the cathode compartment. These gravity sludges can cause siteshort circuiting and loss of power. Higher power must be used than froman equivalent charge balanced site and fouling of the cathodes resultsin a power inefficiency. Additional volumes of hazardous wastes areproduced as complex metal precipitates and sludges. Site hot spots ofheavy metals and areas which contain low electrical gradients are notproperly regenerated. Periodic cleaning of electrodes which involve siteshutdown and produce hazardous wastes are a normal feature of standardelectrokinetic soil/waste sites. All these activities extend remediationtime and in many cases available funding runs out and the site is onlypartly regenerated. The production of large quantities of hazardousmetal wastes require substantial funds for disposal of these wastes.

The major activities that account for the superior heavy metal removalswhen compared to the basic electrokinetic process include:

(1) The soil pH remains totally in the acid state and prevents thepotential calcium precipitation which will reduce the flow of acidicliquid through the site and reduce the efficiency of heavy metalremovals.

(2) There are no heavy metals in the liquid leaving the anode as thesewere captured by the proprietary resin bed technology. The rate ofdesolubilization of metals from either precipitated or crystallinestructures in the soil is accelerated.

(3) The acid generated by the anode in a standard electrokineticreaction moves through the soil bed at a typical horizontal rate of 10cm/day in a clay site. The circulating pumped liquid of the presentinvention migrates across the soil bed at 200 cm/day to 500 cm/day.

(4) The circulating acid flow from the anode moves through the site at10 gph-1,000 gph and is monitored and adjusted by the pH controller toinsure maximum heavy metals removal from the soils. Heavy metals areremoved at a minimum of 5-10 times the removal rates of conventionalelectrokinetic soil remediations.

(5) In conventional electrokinetic remediations, cathode pH control isperformed by injection of circulating liquid at the cathode. This issimply a neutralization reaction required to prevent high pH bedplugging at the cathode. The charge balancing process uses the acid toalso reduce the pH at the anode where the acid is used in metaldesolubilization reactions. That permits significant reduction in powerinput to the site, a reduction in potential poisonous gas releases andlower acid requirements for neutralization of hydroxyl ions at thecathode. A further power efficiency was discussed earlier in that thesecondary anode (cathode) has a controlled acidic pH, which preventsprecipitation on the silver electrode and minimizes production ofsludges. The silver electrodes stay clean and negligible quantities ofcathode sludges are produced.

(6) The present invention is ideal for removal of hot spots (high heavymetal concentrations) as well as for removal of heavy metals from areaswhere low voltages and current densities are observed (skipped area ofremediation). The liquids can be concentrated at the anodes andsecondary anodes and quickly remove those anomalies.

The present invention further includes a similar system for the anodewhere anions of interest are pumped from the anode, routed through astrong anion resin bed exchanger, and returned to the cathode. A pHcontrol system is employed to keep the cathode in an acidic condition toprevent precipitation at the cathode. The rate of removal of the anionsfrom the soil bed is greatly accelerated in a similar manner to theheavy metal cations discussed above.

While the invention has been described with reference to specificembodiments, modifications and variations of the invention may beconstructed without departing from the scope of the invention, which isdefined in the following claims.

We claim:
 1. An apparatus for removing heavy metals, cations and complexions acting as cations from media comprising a vessel having an inlet,an outlet, a cation exchange chamber, an untreated media chamberpositioned between the inlet and the cation exchange chamber, and atreated media chamber positioned between the outlet and the cationexchange chamber, at least one cation exchange resin bed provided in thecation exchange chamber, a first membrane separating the untreated mediachamber from the cation exchange chamber, a second membrane separatingthe treated media chamber from the cation exchange chamber, a firstelectrical grid positioned in the untreated media chamber, a secondelectrical grid positioned in the treated media chamber, a removal traphaving a first end connected to the untreated media chamber and a secondend connected to the treated media chamber, and a power source connectedto the first and second electrical grids.
 2. The apparatus of claim 1,further comprising an inlet filter for filtering the media prior toentering the untreated media chamber.
 3. The apparatus of claim 2,wherein the inlet filter is selected from the group consisting of acartridge and a sand bed.
 4. The apparatus of claim 1, furthercomprising an anion exchange chamber connected to the cation exchangechamber and positioned between the first membrane and the secondmembrane, at least one anion exchange resin bed positioned in the anionexchange chamber, a third electric grid positioned in the untreatedmedia chamber above the at least one anion exchange resin bed, and afourth electric grid positioned in the treated media chamber beneath theat least one anion exchange resin bed.
 5. The apparatus of claim 1,further comprising at least one hydrogen vent line extending from thevessel, at least one oxygen line extending from the vessel, a hydrogencaustic scrubber positioned in the at least one hydrogen line, and anoxygen caustic scrubber positioned in the at least one oxygen line. 6.The apparatus of claim 5, wherein scrubbers are made of material highlyresistant to strong acids and bases.
 7. The apparatus of claim 6,wherein scrubbers are made of material selected from the groupconsisting of plastic, lined stainless steel and lined monel-gradesteel.
 8. The apparatus of claim 1, wherein the electrical grids areimpervious to acids and bases.
 9. The apparatus of claim 1, wherein thecation exchange bed further comprises strong acid ion exchange resin.10. The apparatus of claim 9, wherein the resin has a macroporousstructure, is crosslinked with polystyrene and has a functional group.11. The apparatus of claim 10, wherein the functional group is sulfonicacid.
 12. The apparatus of claim 1, wherein the first electric grid is anegative electrode and the second electric grid is a positive electrode.13. The apparatus of claim 1, wherein the removal trap is selected fromthe group consisting of a stationary filter, a portable filter, aseparation device and a partitioned collection system that separatesvaluable metals from invaluable metals.
 14. The apparatus of claim 13,wherein the separation device is a sedimentation unit.
 15. The apparatusof claim 1, wherein the vessel further comprises a container, valves andpipes, wherein the vessel is made of materials selected from the groupconsisting of plastic, non-conducting materials, non-groundingmaterials, metal lined internally with non-conductive coatings, andcombinations thereof.
 16. The apparatus of claim 1, further comprisingcontrols for detecting, monitoring and controlling conditions selectedfrom the group consisting of temperature, breakthrough, turbidity, pH,conductivity, pressure and combinations thereof.
 17. The apparatus ofclaim 1, wherein the first electric grid faces the second electric gridwith a maximum grid surface area of the first grid facing a maximum gridsurface area of the second grid.
 18. An apparatus for removing anionsand complex ions acting as anions from media comprising a vessel havingan inlet, an outlet, an anion exchange chamber, an untreated mediachamber positioned between the inlet and the anion exchange chamber, anda treated media chamber positioned between the outlet and the anionexchange chamber, at least one anion exchange resin bed provided in thecation exchange chamber, a first membrane separating the untreated mediachamber from the anion exchange chamber, a second membrane separatingthe treated media chamber from the anion exchange chamber, a firstelectrical grid positioned in the untreated media chamber, a secondelectrical grid positioned in the treated media chamber, a return linefor returning media from the treated media chamber to the untreatedmedia chamber, and a power source connected to the first and secondelectrical grids.
 19. The apparatus of claim 18, further comprising apump for pumping the media from the treated media chamber to theuntreated media chamber through the return line.
 20. The apparatus ofclaim 18, further comprising a concentrate anion tank connected to theuntreated media chamber.
 21. The apparatus of claim 18, wherein thefirst electric grid is a positive electrode and the second electric gridis a negative electrode.
 22. The apparatus of claim 18, furthercomprising an cation exchange chamber connected to the cation exchangechamber and positioned between the first membrane and the secondmembrane, at least one cation exchange resin bed positioned in thecation exchange chamber, a third electric grid positioned in theuntreated media chamber above the at least one cation exchange resinbed, and a fourth electric grid positioned in the treated media chamberbeneath the at least one cation exchange resin bed.
 23. The apparatus ofclaim 18, further comprising at least one hydrogen vent line extendingfrom the vessel, at least one oxygen line extending from the vessel, ahydrogen caustic scrubber positioned in the at least one hydrogen line,and an oxygen caustic scrubber positioned in the at least one oxygenline.
 24. The apparatus of claim 23, wherein scrubbers are made ofmaterial highly resistant to strong acids and bases.
 25. The apparatusof claim 24, wherein scrubbers are made of material selected from thegroup consisting of plastic, lined stainless steel and lined monel-gradesteel.
 26. The apparatus of claim 18, wherein the electrical grids areimpervious to acids and bases.
 27. The apparatus of claim 18, whereinthe vessel further comprises a container, valves and pipes, wherein thevessel is made of materials selected from the group consisting ofplastic, non-conducting materials, non-grounding materials, metal linedinternally with non-conductive coatings, and combinations thereof. 28.The apparatus of claim 18, further comprising controls for detecting,monitoring and controlling conditions selected from the group consistingof temperature, breakthrough, turbidity, pH, conductivity, pressure andcombinations thereof.
 29. The apparatus of claim 18, wherein the firstelectric grid faces the second electric grid with a maximum grid surfacearea of the first grid facing a maximum grid surface area of the secondgrid.
 30. The apparatus of claim 18, wherein the anion exchange bedfurther comprises strong anion exchange resin having crosslinkedpolystyrene having functional groups.
 31. The apparatus of claim 30,wherein the functional groups comprises quaternary amine.
 32. A methodfor removing heavy metals, cations, and complex ions acting as cationsfrom media, comprising the steps of providing a vessel having an inlet,an outlet, and a cation exchange chamber, providing an untreated mediachamber positioned between the inlet and the cation exchange chamber,and providing a treated media chamber positioned between the outlet andthe cation exchange chamber, providing at least one cation exchangeresin bed in the cation exchange camber, providing a first membraneseparating the untreated media chamber from the cation exchange chamber,providing a second membrane separating the treated media chamber fromthe cation exchange chamber, providing a first electrical gridpositioned in the untreated media chamber, providing a second electricalgrid positioned in the treated media chamber, providing a removal traphaving a first end connected to the untreated media chamber and a secondend connected to the treated media chamber, and providing a power sourceconnected to the first and second electrical grids.